1. Field of the Invention
The present invention is generally related to a marine propulsion device and, more particularly, to an outboard motor with a lubricant management system that maintains a dry sump and a lubricant reservoir by utilizing two pumps which are both driven by the crank shaft of an internal combustion engine.
2. Description of the Prior Art
As is known to those skilled in the art, outboard motors which use four-cycle internal combustion engines present certain problems that are not inherent with two-cycle engines. Since four-cycle engines are, by their nature, larger than two-cycle engines of equivalent horsepower, the location of the sump requires particular care. For example, if the sump of the internal combustion engine is used to store the oil of the engine, placement of the sump within the crank shaft housing creates a particular problem because it places the oil close to the exhaust passages. This can create excessive temperatures in the oil within the sump and generally requires a cooling water system to maintain the oil temperature within acceptable magnitudes. If the sump is placed directly under the internal combustion engine and above the crank shaft housing, a four-cycle internal combustion engine would typically extend too high to be practical. In other words, the internal combustion engine and its cowling would extend significantly above the point about which the engine is intended to be rotated for trimming. If, on the other hand, the sump is located on the sides of the engine, it would be too wide and would likely obscure the boat operator's vision in the aft direction.
To solve these problems, it is well-known to those skilled in the art to provide the four-cycle internal combustion engine with a dry sump in combination with a lubricant reservoir. Oil that drains into the sump, under the influence of gravity, is pumped by a scavenge pump into the reservoir for future use. Another pump, referred to as a pressure pump, draws the lubricant from the reservoir and transmits it through a conduit to regions that require lubrication within the structure of the internal combustion engine. These principles are generally wellknown to those skilled in the art.
U.S. Pat. No. 4,523,556, which issued to Suzuki on Jun. 18, 1985, discloses a four-cycle internal combustion engine for outboard motors. Two embodiments of the lubricating system for four-cycle engines are described. Each of the systems embodies a lubricant sump that is disposed beneath the engine and to which lubricant is returned by gravity. In each of the two embodiments, a buffer volume is provided which receives lubricant when the engine is oriented in other than a desired position so that the oil will flow into the buffer volume rather than being discharged from the sump. The lubricant is returned to the engine from the buffer volume when the engine is again placed in its normal orientation. In one embodiment of this particular system, the buffer volume is provided by the cam shaft chamber of the engine.
U.S. Pat. No. 4,735,590, which issued to Mondek on Apr. 5, 1988, describes a lubrication system for a marine propulsion device. The marine propulsion device comprises a propulsion unit including an internal combustion engine, a pump driven by the engine, a transom bracket for mounting the propulsion unit to the transom of a boat, a fluid reservoir carried by the transom bracket, a fluid cooler carried by the transom bracket for cooling the fluid contained in the reservoir, and a conduit for communicating the cold oil to the pump.
U.S. Pat. No. 4,828,519, which issued to Watanabe on May 9, 1989, describes an outboard motor with an improved lubricating system for its internal combustion engine. The lubricant sump is positioned beneath the engine, and oil is returned to the sump through a drain opening in a spacer plate that separates the engine from the crank shaft housing. The oil sump and drain opening are configured so that oil will not return from the sump through the drain opening to the engine when the outboard motor is laid on its side edge.
U.S. Pat. No. 5,036,804, which issued to Shibata on Aug. 6, 1991, discloses a cooling system for a four-stroke outboard motor. The cooling system is used for a four-cycle internal combustion engine that is utilized as a power plant for an outboard motor. The cooling system is designed so that coolant is first delivered to cool an exhaust manifold in the cylinder block. Then the exhaust ports of the cylinder head and the other cylinder head components and then the cylinder block cooling jacket surrounding the cylinder bores.
U.S. Pat. No. 5,037,340, which issued to Shibata on Aug. 6, 1991, describes a lubricating device for a four-stroke outboard motor. A number of embodiments of outboard motors powered by four-cycle internal combustion engines have dry sump lubrication systems wherein the external oil reservoir is positioned externally of the engine. In some embodiments, the reservoir is contained directly in the power head and in other embodiments the reservoir is contained externally of the outboard motor. The use of external positioning of the lubricant reservoirs from the crank shaft housing permits the use of a large expansion chamber for the exhaust system in the crank shaft housing. In one embodiment, a pair of expansion chambers are provided.
U.S. Pat. No. 5,072,809, which issued to Shibata on Dec. 17, 1991, describes a lubricating device for a four-stroke outboard motor. The dry sump lubrication system includes a scavenge pump for drawing lubricant drained from the engine lubricating system through an inlet port and returning it to a dry sump reservoir through an outlet port and a pressure pump that draws lubricant from the dry sump lubricant reservoir through an inlet port and delivers it to the engine lubricating system through an outlet port. At least one of the ports of each of the pumps is positioned above the normal lubricant level in the lubricant reservoir when it is filled with the normal volume of lubricant so as to ensure that lubricant will not drain back into the engine when the pump system is not operating. Various arrangements for achieving this result and for cooling the lubricant system are described in U.S. Pat. No. 5,072,809.
U.S. Pat. No. 5,149,287, which issued to Koike on Sep. 22, 1992, describes a separate oiling system for an outboard motor. The lubricating system for an outboard motor has a lubricant delivery tank mounted on the outboard motor which is replenished by a pumping system from a separate lubricant storage tank contained within the hull of an associated watercraft. The circuit for controlling the pump includes a trim angle sensor which is mounted on the lubricant delivery tank for preventing operation of the pump when a trim angle change would incorrectly indicate a need for the addition of lubricant to the lubricant delivery tank.
U.S. Pat. No. 5,163,394, which issued to Koishikawa et. al. on Nov. 17, 1992, describes an engine with horizontal cylinders and an outboard engine assembly. The engine assembly includes a cylinder block with at least one horizontal cylinder defined therein, an oil pan disposed downwardly of the cylinder block, a cylinder head coupled to the cylinder block, and a head cover coupled to the cylinder head. The engine assembly also includes a valve operating mechanism chamber defined jointly between the cylinder head and the head cover, a lubricating oil supply passageway for supplying lubricating oil from the oil pan to at least the valve operating mechanism chamber, and a lubricating oil return passageway for returning lubricating oil from at least the valve operating mechanism chamber to the oil pan. The lubricating oil return passageway has openings for introducing lubricating oil from the valve operating mechanism chamber. The openings are defined in inner surfaces, respectively, of the cylinder head and the head cover which face a bottom of the valve operating mechanism chamber.
U.S. Pat. No. 5,215,164, which issued to Shibata on Jun. 1, 1993, discloses a lubricating device for a four-stroke outboard motor. The dry sump lubrication system includes a scavenge pump for drawing lubricant drained from the engine lubricating system through an inlet port and returning it to a dry sump reservoir through an outlet port and a pressure pump that draws lubricant from the dry sump lubricant reservoir through an inlet port and delivers it to the engine lubricating system through an outlet port. At least one of the ports in each of the pumps is positioned above the normal lubricant level in the lubricant reservoir when it is filled with the normal volume of lubricant so as to ensure that lubricant will not drain back into the engine when the pump system is not operating. Various arrangements for achieving this result and for cooling the lubricant are described in U.S. Pat. No. 5,215,164.
U.S. Pat. No. 5,439,404, which issued to Sumigawa on Aug. 8, 1995, describes a cooling system for an outboard motor. The lubricating reservoir bends into the crank shaft housing and is surrounded by an opening and is surrounded by an open trough-like manifold to which cooling water is delivered from the engine. This manifold has lower restricted openings that direct the coolant to the outer peripheral wall of the oil pan of the lubricant reservoir. The water level is maintained by a weir-like structure, and the water that overflows the weir is also directed toward the outer surface of the lubricant reservoir.
U.S. Pat. No. 5,640,936, which issued to Hudson on Jun. 24, 1997, discloses a removable oil reservoir for dry sump internal combustion engines. The removable oil tank and oil filter for a four-cycle dry sump internal combustion engine has particular utility in marine applications. A support for the tank is attached to or near the engine, and the oil tank is held in engagement with the support by mechanical quick disconnect retainers. Oil lines connecting the tank and the engine oil circulating system are connected by quick disconnect fluid connectors. One portion of the quick disconnect fluid connectors may be fixedly attached to a support for the tank in a position where they assist in supporting the oil tank when the connectors are joined.
The United States patents described immediately above are hereby incorporated by reference herein.
As is well known to those skilled in the art and described in the patents discussed above, it is common to provide a dry sump and a second lubricant reservoir for four-cycle internal combustion engines used in outboard motors. The inherently larger four-cycle engines, compared to two-cycle engines of similar power rating, require that the various components of the internal combustion engine be efficiently positioned to avoid making the outboard motor excessively high or wide. In addition, the lubricating oil must be maintained at a suitable temperature to avoid overheating or overcooling. The patents described above illustrate many different approaches known to the skilled artisan. In view of the prior art, it would be significantly beneficial if the scavenge pump and pressure pump could be advantageously located within the structure of the outboard motor to efficiently pump lubricant from the dry sump to the lubricant reservoir and from the lubricant reservoir to the regions of the internal combustion engine that require lubrication. It would also be significantly beneficial if the lubrication system could be constructed to take advantage of the efficiently located pressure and scavenge pumps while also avoiding the drainage of lubricant back into the engine when the outboard motor is tilted significantly from its normal operating position, either during use or when it is removed from a watercraft and stored.